Centrifugal pumps are well known and widely used in a variety of industries to pump fluids or liquid/solid components of fluid mixtures. Centrifugal pumps, particularly those of the pitot type, generally comprise a pump housing having an inlet and an outlet and a rotor assembly which rotates within the pump housing by means of a drive unit. The fluid inlet and the fluid discharge in conventional pitot pumps are positioned in parallel orientation on the same side of the pump housing, in a side-by-side arrangement. Oftentimes, the inlet is concentric with the fluid discharge.
Fluid is directed through the pump inlet into the rotor chamber and as the rotor assembly rotates, the fluid is directed toward the inner peripheral surface of the rotor chamber as a result of centrifugal forces. The fluid is intercepted by a stationary pitot tube and fluid moves through the inlet of the pitot tube and through the pitot tube arm toward the discharge outlet of the pump.
Typical centrifugal pumps of the pitot tube type are disclosed in U.S. Pat. No. 3,822,102 to Erickson, et al.; U.S. Pat. No. 3,960,319 to Brown, et al.; U.S. Pat. No. 4,161,448 to Erickson, et al.; U.S. Pat. No. 4,280,790 to Crichlow; U.S. Pat. No. 4,332,521 to Erickson and U.S. Pat. No. 4,674,950 to Erickson. In the pumps disclosed in the referenced patents, the fluid inlet and discharge outlet are positioned on the same side of the pump casing. The inlet of the rotor surrounds the entry point of the pitot tube into the interior of the rotor. Pitot tube pumps of this conventional construction can experience various disadvantages, including limitations on pump sizing and design to maximize pump efficiencies, poor or inefficient balancing of the very heavy rotor, bearing load designs that compromise the ability to resist the moment of an overhung rotor and seal leakage issues. As a result of these limitations, pump efficiencies can be compromised and the life of the pump can be shortened.
Other types of centrifugal pumps of the pitot type are disclosed in U.S. Pat. No. 3,791,757 to Tarifa, et al.; U.S. Pat. No. 4,875,826 to Readman; U.S. Pat. No. 2,376,071 to Miess and U.S. Pat. No. 3,384,024 to King. These patents disclose varying designs of pumps that employ one or more pitot tubes in a rotor. They disclose varying configurations for directing fluid into the rotor and discharging fluid from the rotor, typically in parallel directions on a single side of the pump, or they disclose ingress and egress of fluid at perpendicular angles to each other. U.S. Pat. No. 3,791,757 to Tarifa, et al. and U.S. Pat. No. 4,875,826 to Readman also disclose pump configurations where fluid enters a rotor from one direction of the rotor and exits from an opposing side of the rotor. However, these designs, due to the configuration of the pumps, result in high or significantly ineffective NPSH (net positive suction head). They are also configured such that some of the pumps lack effective hydraulic axial thrust balance, and many of the pumps are unable to operate at high speeds or adequate pressures. These prior known pumps can also be very complex and, therefore, costly to build and maintain, while also resulting in poor pump performance.